weird rash that won't go away

Hello, I've had some discoloration on my skin for few months now on my inner thigh.  It started this winter - in order to stay warm, I had a space heater on close to my legs.  I developed discoloration; -red lines surrounding normal-colored skin in misshapen circles - [they look like clouds for lack of a better description.]  It was bright red at first, and has faded but is still visible months later.  The area has never been painful or itchy.  Is this some kind of heat rash?  I've never seen anything like this before.

Thank you.